1. Field of the Invention
The present invention pertains to the field of medical radiation dosimetry. More particularly, the present invention pertains to the field of medical radiation dosimetry systems and methods which utilize scintillating fibers for radiation measurement.
2. Description of the Related Art
High energy charged particle and photon radiation can penetrate deeply into solid and liquid matter. Their energy loss leads to ionization along the way. This ionization is useful in many applications including medical therapy. As one example, medical radiation therapy, at Low Dose Rate (LDR) and at High Dose Rate (HDR), has proven beneficial for killing cancer in humans. Its use has also been recently approved by the USA FDA for limited IntraVascular Brachytherapy (IVB) where HDR irradiation of blood vessels opened by balloon angioplasty can often prevent the frequent re-closing of the treated blood vessel (restenosis).
However, current medical radiation dosimetry systems and methods have a number of shortcomings. To begin with, most radioactive seeds for LDR and HDR therapy are not directly measured or verified at the hospital prior to use. Additionally, verification of the seed strengths by the seed maker or supplier or hospital is often carried out on only a statistical sample of about 10% of such seeds because of the long time needed for standard dosimetry.
Applicant is aware of the following related art documents which show the state-of-the-art in e.g. scintillating fiber dosimetry systems, all of which are incorporated by reference herein: McCollough, Kevin P., xe2x80x9cA Scintillation Detector for the Calibration of Individual Seeds within an Ir-192 Ribbonxe2x80x9d, Radiation Oncology, Biology, Physics, Volume 24 Supplement 1, 1992, page 288; U.S. Nuclear Regulatory Commission Report NUREG/CR-5223 entitled xe2x80x9cScintillating Fiber Detector for In-Vivo Endoscopic Internal Dosimetryxe2x80x9d, published October 1988; Beddar, A. S., et al, xe2x80x9cWater-equivalent plastic scintillation detectors for high-energy beam dosimetry: I. Physical characteristics and theoretical considerationsxe2x80x9d, Phys. Med. Biol., 1992, Vol. 37 No. 10, pp. 1883-1900; Flxc3xchs, D. et al., xe2x80x9cDirect reading measurement of absorbed dose rate with plastic scintillatorsxe2x80x94The general concept and applications to ophthalmic plaque dosimetryxe2x80x9d, Med. Phys. 23 (3), March 1996, pages 427-434; St. Clair, Shaun et al., xe2x80x9cAn In-Theatre Source Strength Verification System for I-125 Rapid Strand Seedsxe2x80x9d (Department of Medical Physics, Yorkshire Centre for Clinical Oncology, Cookridge Hospital, U.K.); U.S. Pat. No. 5,704,890 entitled xe2x80x9cReal Time Sensor for Therapeutic Radiation Deliveryxe2x80x9d; Japanese Published Unexamined Patent Application 10-213663 entitled xe2x80x9cLocal Dosimeterxe2x80x9d; U.S. Pat. No. 5,880,475 entitled xe2x80x9cScintillation Fiber Type Radiation Detectorxe2x80x9d; U.S. Pat. No. 5,905,263 entitled xe2x80x9cDepth Dose Measuring Devicexe2x80x9d; U.S. Pat. No. 6,151,769 entitled xe2x80x9cMethod of Making a Scintillator Waveguidexe2x80x9d; and Japanese Published Unexamined Patent Application 2001-56381 entitled xe2x80x9cLocal Radiation Amount Measuring Device and Medical Device Equipped Therewithxe2x80x9d; P.C.T. International Patent Application WO 01/93943 entitled xe2x80x9cAutomated Radioisotope Seed Loader System for Implant Needlesxe2x80x9d; P.C.T. International Patent Application WO 01/93945 entitled xe2x80x9cAutomated Radioisotope Seed Cartridgexe2x80x9d; U.S. patent application Publication 2001/0053870 entitled xe2x80x9cMethod for Analyzing Amount of Activityxe2x80x9d.
Of particular interest, the McCollough article describes a scintillation detector in which a short (3 mm length) scintillating fiber is coupled to a photomultiplier tube (PMT) face. Individual seeds within an Ir-192 ribbon can be scanned while the ribbon is translated under the scintillator.
The two P.C.T. International Patent Applications reveal an automated radioisotope seed loader which includes a xe2x80x9cproportional counter type radiation sensor 42xe2x80x9d to detect the radiation levels in the seeds as they are loaded from a cartridge to a needle and to verify the radiation strength of the radioisotope seeds.
The U.S. patent application Publication reveals in FIG. 28 a seed-spacer train assembly module which includes a scintillating sheet 209 that emits light when hit by radiation from a seed in a tube 148.
There remains a need for a compact, accurate, and fast-acting scintillating fiber dosimetry system which is particularly adapted for medical applications.
It is a first object of the invention to provide a compact, accurate, and fast-acting scintillating fiber dosimetry system which is particularly adapted for medical applications.
It is another object of the invention to provide a scintillating fiber dosimetry system and associated method which can be used at a hospital or radiation treatment facility for Quality Assurance (QA) in verifying radiation dose levels.
It is a further object of the invention to provide a scintillating fiber dosimetry system which is particularly adapted to measure the radiation produced by a number of seeds pre-loaded within a needle or cartridge.
It is a still further object of the invention to provide a scintillating fiber dosimetry system which is useful for calibrating 100% of the seeds in a holder in less time than it currently takes to calibrate 10% of the seeds in the holder.
It is a still further object of the invention to provide a scintillating fiber dosimetry system which is useful for detecting the spacers between the seeds in a pre-loaded seed needle or cartridge.
In one respect the invention relates to a dosimetry system comprising: a rigid structure; a scintillating fiber mounted on the rigid structure in a substantially relatively immovable manner, the scintillating fiber having a cylindrical peripheral surface and first and second end surfaces; a light intensity measuring device attached to the rigid structure in a substantially relatively immovable manner; coupling means for optically coupling the first end surface of the scintillating fiber to an active portion of the light intensity measuring device; wherein the light intensity measuring device produces an output signal in accordance with an amount of light generated by the scintillating fiber; and wherein the scintillating fiber is mounted on the rigid structure in such a manner that a longitudinal axis of the scintillating fiber extends in a direction away from the active portion of the light intensity measuring device, with a distance between the active portion of the light intensity measuring device and the second end surface of the scintillating fiber being between substantially 15 mm and substantially 200 mm, and wherein a portion of the cylindrical peripheral surface of the scintillating fiber is unshielded and accessible; and wherein radiation measurement is carried out adjacent the accessible portion of the cylindrical peripheral surface of the scintillating fiber.